Q: I'm not a teetotaler - in fact, I often drink a glass or two of Chablis with dinner-and I've never had a problem with headaches or hangovers until recently. I've gone to several cocktail parties lately and had a mixed drink made with bourbon. The next morning I have an intense headache even though I know I didn't drink too much. What's causing this pain?

Dr. Donnica: Bourbon, scotch and other dark-colored liquors-even red wine and beer--contain congeners, compounds that lend alcohol its color and flavor, and form naturally during the alcohol fermentation process. Experts aren't sure exactly why, but some people have a lower tolerance to congeners, and for them - and you, it seems - the substances can cause head-banging headaches or migraines. As a general rule, light-colored alcohols like gin and vodka contain fewer congeners, so you're less likely to get a headache after one or two cocktails made with them or with white wine. Also as a general rule: if you get this reaction repeatedly, it will continue to happen if you continue to consume these types of alcohol. Another potential contributor to your headache is dehydration, which is common after a night sipping cocktails. So match your cocktail intake glass-for-glass with water. Enjoy the hors d'oevres, too, because alcohol's more apt to cause more problems on an empty stomach. And definitely don't drive yourself home.